Arteriovenous malformations (AVMs) are defects of the circulatory system that are generally believed to arise during embryonic or fetal development or soon after birth; They are comprised of snarled tangles of arteries and veins; AVMs of the brain or spinal cord (neurological AVMs) are believed to affect approximately 300,000 Americans; these abnormalities cause symptoms that vary greatly in severity; For a small fraction of the individuals within this group, such symptoms are severe enough to become debilitating or even life-threatening;

Seizures and headaches are the most generalized symptoms of AVMs, but no particular type of seizure or headache pattern has been identified; Seizures can be partial or total, involving a loss of control over movement, convulsions, or a change in a person’s level of consciousness; Headaches can vary greatly in frequency, duration, and intensity, sometimes becoming as severe as migraines; Sometimes a headache consistently affecting one side of the head may be closely linked to the site of an AVM; AVMs also can cause a wide range of more specific neurological symptoms that vary from person to person, depending primarily upon the location of the AVM; Such symptoms may include muscle weakness or paralysis in one part of the body; a loss of coordination (ataxia) that can lead to such problems as gait disturbances; apraxia, or difficulties carrying out tasks that require planning; dizziness; visual disturbances such as a loss of part of the visual field; an inability to control eye movement; papilledema (swelling of a part of the optic nerve known as the optic disk); various problems using or understanding language (aphasia); abnormal sensations such as numbness, tingling, or spontaneous pain (paresthesia or dysesthesia); memory deficits; and mental confusion, hallucinations, or dementia; One of the more distinctive signs indicating the presence of an AVM is an auditory phenomenon called a bruit: the rhythmic, whooshing sound caused by excessively rapid blood flow through the arteries and veins of an AVM; Symptoms caused by AVMs can appear at any age, but because these abnormalities tend to result from a slow buildup of neurological damage over time they are most often noticed when people are in their twenties, thirties, or forties; If AVMs do not become symptomatic by the time people reach their late forties or early fifties, they tend to remain stable and rarely produce symptoms; In women, pregnancy sometimes causes a sudden onset or worsening of symptoms, due to accompanying cardiovascular changes, especially increases in blood volume and blood pressure; The damaging effects of a hemorrhage are related to lesion location; Bleeding from AVMs located deep inside the interior tissues, or parenchyma, of the brain typically causes more severe neurological damage than does hemorrhage by lesions that have formed in the dural or pial membranes or on the surface of the brain ; intracerebral or parenchymal hemorrhage; bleeding within the membranes or on the surface of the brain is known as subdural or subarachnoid hemorrhage) Thus, location is an important factor to consider when weighing the relative risks of surgical versus non-surgical treatment of AVMs; ------------------------[NIH/NIND 2007]----------------

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